1. Field of the Invention
The present invention relates to a semiconductor-substrate processing apparatus used in photolithography, which is a process of manufacturing a semiconductor device, and mainly in a step of stripping a photoresist that is applied onto a semiconductor substrate surface and a step of removing organic substances adhered onto the semiconductor substrate surface.
2. Description of the Related Art
In the manufacturing of a semiconductor device through use of a semiconductor substrate, there has been performed a step of stripping a photoresist applied onto a semiconductor substrate surface off from the substrate surface. There has also been performed processing of immersing the semiconductor substrate into a chemical solution, which is made by heating a mixed liquid of sulfuric acid and a hydrogen peroxide solution up to a temperature of 120 degrees Celsius or more, in order to remove organic substances adhered onto the semiconductor substrate surface, and then performing cleaning using pure water and drying. This is a technology using the fact that substances on the semiconductor substrate surface, e.g., the photoresist are dissolved or stripped by substances having extremely high oxidizability, e.g., peroxydisulfuric acid that is generated through reaction between the sulfuric acid and the hydrogen peroxide solution.
Further, as an alternative measure, there has been proposed a technology that attains the same effect as that achieved by the mixed liquid formed of the sulfuric acid and the hydrogen peroxide solution. In this technology, there is used a substance having high oxidizability, e.g., peroxydisulfuric acid that is generated through reaction between sulfuric acid and ozone gas. The reaction is caused by injecting the ozone gas into a high-temperature sulfuric acid and then introducing the sulfuric acid and the ozone gas into a processing tank (see, for example, Japanese Patent Application Laid-open H11-174692).
However, when processing is performed to the semiconductor substrate in the apparatus disclosed in Japanese Patent Application Laid-open H11-174692, a problem arises as described below. In particular, at first, the photoresist film that is stripped is collected by a filter, but a large amount of resist peels off right after the stripping. Therefore, there is a fear in that the filter may be contaminated by the resist, thereby lowering its collecting performance. This leads to resist that cannot be collected being adhered to the wafer again in form of fine particles. Further, there is a limit on concentration in which ozone can be dissolved in the chemical solution using a permeation membrane. Therefore, there is a problem in that parts of the resist may be difficult to strip depending on the pattern that is transferred onto the semiconductor substrate surface, and that the resist may remain on the substrate surface even when the processing is continued for a long time.